’s trying to make it around the block four times, as well as the 36-minute 10K runner who’s training for a first marathon with long runs that stretch to 12 miles, then 16, then 20.The gradual-adaptation principle is deeply rooted in human physiology, and has

ran 2:42:24 in 1975, and Joan Benoit Samuelson ran 2:22:43 in 1983. ("World best" was the euphemism instead of "world record" for road-race performances before January 1, 2004.) This year saw a course record set in the men's race, but, at 2:07:14

crashed. He now believes he did too many hard 20-milers in the heat. "I was exhausted from the first step of the marathon," he says. He finished 15th in 2:14:19.HydrationEveryone knows drinking fluids is supposed to help you run faster. But you have

the result.“I covered 18-23 miles in my long training runs,” says Strand, “and I did the last 9-14 miles at marathon pace or faster. That was much faster than my previous long-run efforts of 17-22 miles at whatever pace I felt like running.”This kind